DCT
1:25-cv-00659
Fujirebio Diagnostics Inc v. Quanterix Corp
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Fujirebio Diagnostics, Inc. (Pennsylvania)
- Defendant: Quanterix Corporation (Delaware)
- Plaintiff’s Counsel: Duane Morris LLP
- Case Identification: 1:25-cv-00659, D. Del., 05/28/2025
- Venue Allegations: Venue is alleged to be proper in the District of Delaware because Defendant is a corporation organized under the laws of Delaware and maintains a registered agent in the district.
- Core Dispute: Plaintiff seeks a declaratory judgment that its diagnostic assays for detecting Alzheimer's-related biomarkers do not infringe Defendant’s patent directed to methods for measuring tau protein in bodily fluids.
- Technical Context: The technology concerns highly sensitive immunoassays capable of detecting extremely low concentrations of protein biomarkers, such as tau protein in blood, to diagnose and monitor neurological conditions like Alzheimer's disease.
- Key Procedural History: The complaint for declaratory judgment was filed following a series of public statements and a direct communication from Defendant Quanterix asserting that parties measuring tau protein, including users of Plaintiff Fujirebio's assays, risk infringing the patent-in-suit. The complaint alleges that during patent prosecution, the applicant and examiner mutually understood the patent to be limited to a specific type of assay (SIMOA), a point which may be raised to argue for a narrow claim scope.
Case Timeline
| Date | Event |
|---|---|
| 2011-04-12 | ’092 Patent Priority Date |
| 2022-03-15 | ’092 Patent Issue Date |
| 2024-03-20 | LabCorp announces test using Fujirebio's assay |
| 2024-03-22 | Quanterix issues press release concerning the ’092 Patent |
| 2024-03-25 | Quanterix holds conference call discussing infringement risk |
| 2024-05-02 | Quanterix sends letter to Fujirebio regarding the ’092 Patent |
| 2025-01-16 | Quanterix and Fujirebio enter into a Non-Disclosure Agreement |
| 2025-05-01 | Fujirebio sends notice of termination for the NDA |
| 2025-05-15 | NDA termination becomes effective |
| 2025-05-16 | FDA clears Fujirebio's Lumipulse Plasma Ratio Assay |
| 2025-05-28 | Complaint for Declaratory Judgment filed |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 11,275,092 - "Methods Of Determining A Treatment Protocol For And / Or A Prognosis Of A Patient's Recovery From A Brain Injury"
- Patent Identification: U.S. Patent No. 11,275,092, "Methods Of Determining A Treatment Protocol For And / Or A Prognosis Of A Patient's Recovery From A Brain Injury," issued March 15, 2022.
The Invention Explained
- Problem Addressed: The patent's background section identifies a need for improved methods to diagnose and track brain injuries. It notes that while biomarkers like tau protein are known indicators, their concentrations in blood are often "extremely low" and "not reliably measurable by typical conventional immunoassays," making blood-based testing difficult (’092 Patent, col. 2:1-4).
- The Patented Solution: The invention provides methods for determining a patient's prognosis or treatment protocol by measuring the concentration of tau protein in a blood-derived sample using a highly sensitive assay. The specification describes achieving this sensitivity by using a "single molecule array" (SIMOA) technology, which involves capturing and segregating individual protein molecules into millions of femtoliter-sized reaction wells to enable digital, single-molecule counting (’092 Patent, Abstract; Fig. 1A; col. 21:31-22:24).
- Technical Importance: This technology enables the use of a simple blood test, which is less invasive than collecting cerebrospinal fluid (CSF), to obtain clinically relevant information about neurological damage, a goal previously hampered by the low concentration of such biomarkers in blood (’092 Patent, col. 5:35-50).
Key Claims at a Glance
- The complaint seeks a declaratory judgment of non-infringement as to all claims of the ’092 Patent, with a focus on its single independent claim, Claim 1 (Compl. ¶¶ 40, 54).
- Independent Claim 1 Essential Elements:
- A method of producing a bodily fluid sample... containing an analytically quantified amount of endogenous tau protein, comprising:
- (A) obtaining a volume of bodily fluid comprising blood, or a blood component selected from plasma and serum,
- (B) diluting the volume of bodily fluid, and
- (C) quantifying through the use of an analytical protein concentration measurement assay a concentration of tau protein in the volume of bodily fluid;
- wherein the quantified concentration is less than about 5 pg/ml, and the assay's limit of quantification is less than about 0.2 pg/mL.
III. The Accused Instrumentality
Product Identification
- The complaint identifies the "Lumipulse Tau Assays," which collectively refers to the "Lumipulse G pTau 217 Plasma Assay" and the "Lumipulse G pTau 217/ß-Amyloid 1-42 Plasma Ratio Assay" (Compl. ¶11, ¶14). These products consist of the "LUMIPULSE G1200 Analyzer" and a disposable "pTau cartridge" (Compl. ¶36).
Functionality and Market Context
- The accused assays are described as "chemiluminescent enzyme immunoassay" systems used to detect and quantify pTau 217, a form of tau protein, in human blood plasma to aid in the diagnosis of Alzheimer's disease (Compl. ¶¶12, 48). The complaint alleges that, unlike the technology described in the ’092 Patent, these assays operate by quantifying the analyte from an "undiluted sample in a single reservoir," where numerous molecules are analyzed together rather than being isolated (Compl. ¶¶48-49). The "Lumipulse Plasma Ratio Assay" is noted to have received FDA clearance for commercial marketing as the "first in vitro diagnostic device that tests blood to aid in diagnosing Alzheimer's disease" (Compl. ¶13).
IV. Analysis of Infringement Allegations
No probative visual evidence provided in complaint.
- Claim Chart Summary: The following table summarizes Fujirebio's non-infringement theory as presented in the complaint.
’092 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Non-Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| (A) obtaining a volume of bodily fluid comprising blood, or a blood component selected from plasma and serum, | The Lumipulse Tau Assays use human blood plasma. | ¶12 | col. 2:26-28 |
| (B) diluting the volume of bodily fluid, and | The complaint alleges there is no "dilution" of the sample prior to quantification of the analyte; the assays are premised on quantifying analyte using an undiluted sample. | ¶49 | col. 29:10-12 |
| (C) quantifying through the use of an analytical protein concentration measurement assay a concentration of tau protein... | The Lumipulse Tau Assays quantify the concentration of pTau 217 using a chemiluminescent enzyme immunoassay. | ¶¶12, 48 | col. 2:18-23 |
| wherein the analytically quantified concentration ... is less than about 5 pg/ml, and a limit of quantification of the ... assay ... is less than about 0.2 pg/mL. | The complaint concedes that the accused assays can measure pTau 217 "with a limit of detection at or below that claimed in the '092 Patent." | ¶39 | col. 37:35-41 |
Identified Points of Contention
- Technical Question: The central dispute is factual and technical: do the Lumipulse Tau Assays perform the claimed step of "diluting the volume of bodily fluid"? The complaint asserts they do not, alleging the use of an "undiluted sample in a single reservoir" (Compl. ¶¶48-49). The resolution will depend on the technical evidence of how the accused assays operate.
- Scope Questions: The complaint raises a significant claim construction question regarding whether the scope of the claims is limited to the single molecule array ("SIMOA") technology described in the patent's specification. Fujirebio alleges that the patent only discloses SIMOA and that prosecution history confirms this limited scope (Compl. ¶¶41, 46), while Quanterix is alleged to have asserted the patent is "irrespective of platform" (Compl. ¶19).
V. Key Claim Terms for Construction
The Term: "diluting"
- Context and Importance: This term is at the core of Fujirebio's non-infringement argument. The complaint alleges the accused method uses an "undiluted" sample, and therefore does not perform this required step (Compl. ¶49). The interpretation of whether "diluting" is an essential, ordered step, and what actions constitute "diluting," will be critical.
- Evidence for a Broader Interpretation: Quanterix may argue that the term should be given its plain meaning, potentially covering any addition of reagents or buffers to the sample that changes its concentration, regardless of purpose. The claim itself simply recites "diluting the volume of bodily fluid" without further qualification ('092 Patent, col. 37:33).
- Evidence for a Narrower Interpretation: Fujirebio argues that the patent requires three sequential steps, with "diluting" occurring before "quantifying" (Compl. ¶44). It will likely argue that, in the context of the patent, the term refers to the specific pre-analytical dilution required for single-molecule isolation in a SIMOA assay, as described in the specification's examples ('092 Patent, col. 29:10-12, "All samples were pre-diluted 1:4 with a PBS-tween diluent prior to assay.").
The Term: "analytical protein concentration measurement assay"
- Context and Importance: Practitioners may focus on this term because its breadth determines whether the patent covers only the disclosed SIMOA platform or a wider range of technologies, including Fujirebio’s chemiluminescent immunoassay.
- Evidence for a Broader Interpretation: The term itself is generic. Quanterix is likely to argue that it encompasses any assay meeting the functional requirements of the "wherein" clause (i.e., a limit of quantification less than 0.2 pg/mL), regardless of the underlying mechanism.
- Evidence for a Narrower Interpretation: The complaint argues the specification "describes only one type of assay," SIMOA (Compl. ¶41). Fujirebio may argue that the claims should be limited to this disclosed embodiment, especially in light of alleged statements during prosecution that the invention was a "SIMOA assay" (Compl. ¶46).
VI. Other Allegations
Indirect Infringement
- The declaratory judgment action seeks a declaration of non-infringement for direct, contributory, and inducement liability (Compl. ¶54). The complaint notes that Quanterix's allegations target not just Fujirebio, but also its customers (e.g., LabCorp) who perform the allegedly infringing method using Fujirebio's assays (Compl. ¶25). A finding that the method itself does not infringe would defeat claims for both direct and indirect infringement.
Willful Infringement
- While not alleged against the plaintiff, the complaint establishes a basis for potential willfulness allegations should Quanterix file a counterclaim. It details pre-suit knowledge through Quanterix's public statements beginning March 22, 2024, and a specific notice letter sent to Fujirebio on May 2, 2024 (Compl. ¶¶16, 21).
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of claim scope: can the claims, which recite a generic "analytical... assay," be limited to the specific SIMOA platform that constitutes the entirety of the patent's technical disclosure? The court's handling of Fujirebio's argument regarding prosecution history disclaimer will be central to resolving this question.
- A key evidentiary question will be one of infringing action: does the operation of the accused Lumipulse Tau Assays include a step that meets the definition of "diluting the volume of bodily fluid" as required by Claim 1? This will turn on both the court's construction of the term and the factual evidence of how Fujirebio's system processes a sample.
- The case also presents a fundamental question of technological equivalence: is Fujirebio's "chemiluminescent enzyme immunoassay," which allegedly analyzes molecules together in a single reservoir, a fundamentally different method from the patent's disclosed "digital" method of isolating and counting single molecules, thereby placing it outside the scope of the invention?